What is the site complaining about?

Question

PHP

Hello! In the opencart error log, the following errors periodically pop up:
2019-04-13 16:53:39 - PHP Notice: Undefined index: product_id in /var/www/data/www/catalog/controller/module/viewed.php on line 15
2019 -04-13 16:53:39 - PHP Notice: Undefined index: product_id in /var/www/data/www/catalog/model/module/criteo.php on line 17
viewed.php
https://pastebin.com/ 2s5UwgbR
criteo.php
https://pastebin.com/mhrgCYKT
What doesn't he like?

Answer 1

He doesn't like the fact that $this->request->get is missing a value with the key product_id .
Those. Apparently there is no corresponding argument in the GET request.

Answer 2

$this->request->get['product_id']
It's empty here.